1. Field of the Invention
The invention relates generally to an abrasion resistant bend or elbow-like construction and more particularly to an abrasion resistant bend construction for a small pipeline.
2. Description of the Prior Art
The need to move large volumes of a highly abrasive material places great demands on the piping system through which it is conveyed. Various areas of industry encounter these problems as many different abrasive products are moved, e.g., coal, grain, sand and various waste products. Excessive wear is a common occurrence throughout these areas of industry with the problem being especially severe in pipe sections which change the direction of flow.
As is known, upon a change in the direction of flow of a fluid containing abrasive particles, the wall facing the oncoming stream is subjected to a continuous bombardment of such particles. The result is that the outer bends of the pipes in these transport systems are rapidly worn down and the fittings must be patched or replaced at frequent intervals to prevent leakage of dust, contamination of the surrounding atmosphere, et cetera, so as to avoid health hazards as well as explosive situations. The down time and other costs accrued in the need to continually make such repairs represent a substantial economic loss.
In previous attempts to resolve this problem, a variety of approaches have been taken but a wholly satisfactory solution has not resulted from these efforts. Also, in some instances, the approaches which have been taken provide a more satisfactory solution for large diameter, fabricated elbow constructions made of relatively hard material than they do for relatively small diameter bends formed of relatively soft, ductile metal.
As illustrated in U.S. Pat. Nos. 1,246,189 and 3,551,006, one approach has been to provide an elbow with an abrasion resistant lining.
In U.S. Pat. No. 1,211,784, an elbow construction is described which consists of two separate semi-cylindrical sections with the medial portion of one section being enlarged to accomodate a recess into which lining blocks are inserted.
Another approach is illustrated in U.S. Pat. No. 3,977,730 where impact plate is fixed to the outside surface of the outer bend of the pipe elbow.
In U.S. Pat. No. 3,794,359, a pipe elbow fabricated entirely from non-metallic materials is described. The elbow consists of a pair of wear plates of ceramic material having a semi-circular shape and assembled circumferentially in opposing spaced relationship to each other. A resinous grout is disposed in the circumferential space between the opposed wear plates and a fiber-glass reinforced resin provides a cover over the wear plates and grout.
A liner construction for repair of worn elbows is manufactured by A. P. Green Refractories Company, Green Boulevard, Mexico, Mo. 65265. This approach provides ceramic segment liners mitered to fit at the joints and which match the elbow radius. The joints are filled with epoxy to provide an epoxy bond and a steel band, one per segment, extends around the segment liner and the pipe to hold the liner in place. However, a large hole once worn away in the pipe tends to allow the pipe to expand and leakage may develop, particularly with large size, hardened pipe.
A more recent development is illustrated in applicant's prior U.S. Pat. No. 4,130,300 in which there is illustrated a composite pipe elbow formed of welded-together sections of relatively hard steel and having a plurality of ceramic wear liners held in place over an opening at the outside bend portion of the elbow with a frame and cover arrangement to receive and cover the wear liners. While providing a satisfactory abrasion resistant elbow construction for relatively large diameter pipe lines, the composite type elbow of this prior patent depends upon the pipe being formed of relatively hard steel, being formed of individual sections and requiring the forming of an opening in the sections. Also, the forming of the opening allows the pipe to expand where formed and experience has shown the need for a method and construction better adapted to non-hardened, small diameter pipe.
With all of the foregoing prior art in mind, an object of the present invention is to provide an abrasion resistant bend construction for small pipelines, generally in the range of 2 to 8 inches inside diameter, which particularly lends itself to pipelines formed of relatively soft and ductile metal which can be readily bent, is essentially dust-proof and pressure proof over its service life, eliminates the need to form an opening in the elbow prior to installation, takes advantage of the known tendency of ductile, non-hardened steel not to expand such an opening or at a point of wear and eliminates the need to employ epoxy or other bonding materials between the wear liners. Other objects will appear as the description proceeds.